1. Field of the Invention
The present invention relates to a navigation system that searches for a recommended travel path between a departure point and a destination and guides a vehicle along the recommended travel path.
2. Related Art
Conventional navigation systems detect the present position of a vehicle from GPS (global positioning system) signals, and display it on a display device. The navigation systems also search for a recommended travel path from a departure point to a destination, and display it on the display device. The recommended travel path may be determined by using Dijikstra method or similar methods. In this method, each path connecting two nodes is evaluated with respect to required travel cost by referring to road map data and link information stored in a memory device such as a CD-ROM or a DVD. The recommended travel path is determined by connecting links that will require a minimum cost in total, after all the links from the departure point to the destination are evaluated.
The above method sometimes fails to provide a travel path most favorable to vehicle drivers. This is because not all the available roads are stored in the memory device. Further, the drivers sometimes prefer short-cut roads or less crowded roads even though those roads may be narrow or a detour.
It is therefore an object of the present invention to provide a navigation system that is capable of providing a recommended travel path as drivers desire.
According to the present invention, a navigation system searches a recommended travel path from a departure point to a destination, and collects path information of a leaving path that is taken deviating from the recommended travel path in the course of traveling along the recommended travel path so that the leaving path is learned. The system replaces a part of the recommended travel path with the learned leaving path when the leaving path starts and ends at the recommended travel path, so that the recommended travel path is modified to include the leaving path therein when the same departure point and the destination are input next time.